Apparatus for making sheet glass



INVENTORS ATTORNEY Dec. 1, 1942; B. WHITE ETAL APPARATUS FOR MAKINGSHEET emss 2 Sheets-$heet 1 Original Filed larch 30, 1938 Lue-r'k 5.W141 g ma r L m y 5. m.

Dec. 1, 1942. L. B. WHITE arm. 2,303,805

APPARATUS FOR MAKING SHEET GLASS Original Filed March 30, 19578 2Sheets-Sheet 2 INVENTORS A we rr 5 WHITE ATTORNEY Patented Dec. 1, 1942oFHcE APPARATUS FOR MAKING SHEET GLASS Lurty B. White and Forest S.Tharp, Clarksburg, W. Va., assignors to Pittsburgh Plate Glass Company,a corporation of Pennsylvania Refiled for abandoned application SerialNo.

198,868, March 30, 1938.

This application March 24, 1939, Serial No. 263,925

10- Claims.

The invention relates to apparatus for making sheet glass .by a processin which the glass sheet is drawn vertically from a drawing tank orforehearth. The invention described herein includes that disclosed inour abandoned application, Serial No. 1%,868, filed March 30, 1938, andthe specification and drawings herein presented are substituted forthose of said abandoned application. The tank is provided with a topwith an opening extending transversely thereof, through which the sheetis drawn. Cooling boxes lie in the opening on each side of the sheetadjacent the base of the sheet for chilling the glass, in order topermit the drawing of a sheet of a given thickness at a higher rate ofspeed than would be possible without the coolers. The chilling of theglass is due, in part to the coolers and in part to the exposure of thesurface of the bath to the atmosphere at each side of the line of draw.In drawing a sheet under these conditions, it has been found that thesheet is somewhat thicker at its central portion than at its sides, andto avoid this difficulty, it has been customary to reduce the chillingeffect of coolers at the central portion of the sheet by hangingtransite shades or pads on the centralportions of the coolers, so thatthey lie between this portion of the coolers and the glass sheets.

We have found that the difficulty can be overcome in another way, andone which will permit of a higher drawing speed. Briefly stated, thisconsists in modifying the shape of the drawing opening, so that thecooling effect of the atmosphere at the side portions of thebath isincreased.

The edges of the opening are defined by the horizontal flanges of the Lblocks at each side of the line of draw, and in accordance with thepresent improvement, these flanges, instead of having straighth edgesparallel to the line of draw, taper or incline away from the line ofdraw from the center of the tank toward the edges thereof. This gives asheet of uniform thickness and an increase in drawing speed ofapproximately 25 per cent, since no shielding of the central portions ofthe coolers is required.

Certain embodiments of the invention are illustrated in the accompanyingdrawings, where- Figure l is a fragmentary vertical section through adrawing tank or forehearth. Fig. 2 is a diagrammatic plan view of thedrawing tank. Fig. 3 is a bottom plan of one of the L blocks. Fig. 4 isa bottom plan of another form of L block.

Referring to the drawings, 5 is the end wall of the meltin tank, fromwhich glass is supplied to the forehearth 6; 1 is the end wall of theforehearth; and 8, 8 are the side walls thereof (Fig. 2). A drawbar 9extends transversely of the forehearth from one side to the other tofacilitate the drawing of the glass sheet ill, and a cut off and skinbar I I also extends transversely of the forehearth at its entrance end.The glass sheet It is drawn continuously from the bath by means of thepairs of rolls l2 in the leer casing l3, and these rolls, together withthe draw bar 9, define the plane of drawing in which the sheet glass H3is upwardly drawn. A pair of cooling boxes it, Hi through which water iscirculated extend transversely of the forehearth above the bath andassist in chilling the surface thereof, as is common in the art. Thesecoolers are shown diagrammatically in Figs. 1 and 2.

The top or cover of the forehearth is made up of the upper side of thebar I l, the plates l5 and it and the L blocks l'i, ll, the spacebetween the horizontal flanges i8, i8 of the L blocks constitilting thedrawing opening. The upper portions of the L-blocks are in the form ofupright flanges lta and, therefore, each L-block is somewhat similar inshape to an angle iron. This portion of the bath is chilled, due toradiation and to cooling contact with the atmosphere. As heretoforepointed out the glass sheet being drawn would run thicker at its centralportion than at its edges, if the edges of the horizontal flanges i8,iii of the L blocks were parallel'to the sheet and to each other, and ifthe drawing opening were of uniform width from one side of theforehearth to the other. The L blocks, the lower structure of the leerI3 and the adjacent cooperating parts of the apparatus structure form asocalled drawing chamber 30 through which the glass sheet passesupwardly during the first stages of the drawing operation and thevertical sheet glass during suchoperation is disposed across thischamber between th vertical planes defining the side walls 8. With theexception of the shape of the L blocks ll, the arrangement of theelements of the apparatus structure defining the space from the moltenbath up to the leer casing i3 is more or less conventional and issimilar to that shown in Fig. 1 of patent to Koupal et al. No. 1,598,729of September 7, 1926.

This diificulty, which was a disadvantage in previously knownconstructions, is overcome, as will be seen by referenceto Figs. 2 and3, by howing the flanges l8, l8 towardthe line .of' draW,.

as indicated at I9, sothat the width A of the drawing opening,opposite-.thecen-ter .ofithcsheet,

is less than the dimensions B, B at the points 20, 2|] near the sides ofthe forehearth. In other words, the lower surface of each L block (Figs.1 and 3) is disposed at a predetermined distance above and substantiallyparallel to the upper surface of the bath of molten glass. Since theintermediate portion of the lower surface of each L block has a greaterwidth, heat absorption in the lower side of the L block from the moltenglass is greater and more concentrated at this intermediate portion thanthe heat absorption toward the narrower end portions of the L block. Asa result, the glass is chilled more, due to radiation, opposite the sideportions of the sheet than at the central portion, and the tendency ofthe glass to draw thicker at the center of the sheet, than at the sides,is avoided. The requirement of placing shielding pads on the coolingboxes l4, l4 opposite the center of the sheet, is therefore avoided, andit is possible to draw a sheet of glass of uniform thickness from edgeto edge at a higher rate of speed, then has heretofore been possible. Inpractice, the distance A is about 3 inches less than the distances B, B,but this may vary within certain limits, depending on the width of theforehearth and other conditions.

Fig. 4 illustrates another form. of construction, in which the manner ofbowing the edge of the horizontal flange 2| of the L=block is changed inthat the lines 22, 22 aresubstantially straight instead of bein curvedand these lines extend closer to the ends of the block than is the casewith the curved line of Fig. 3. While, as illustrated and described, thehorizontal flanges of the L blocks define the drawing opening, theinvention is not limited to the use of L blocks, as any other form ofcover members for the bath might be employed at the sides of the drawingopening for defining such opening.

We claim:

1. In an apparatus including a tank containing a' molten glass bath andalso including a drawing chamber through which sheet glass is adapted tobe drawn upwardly in a predetermined plane, means for drawing the sheetglass upwardly from the glass bath with its plane of drawing disposedtransversely of the tank, said drawing chamber including a refractoryblock extending above the bath transversely of the tank on each side ofthe plane of drawing, said block having an inner edge facin the plane ofdrawing and bowed centrally and laterally toward said plane of drawing,the inner block-edge and plane defining between them a space increasingin width in opposite directions from its central portion toward oppositesides of the tank.

2. In an apparatus including a tank containing a molten glass bath andalso including a drawing chamber through which sheet glass is adapted tobe drawn upwardly in a predetermined plane, means for drawing sheetglass upwardly from the glass bath with its plane of drawing disposedtransversely of the tank, said drawing chamber including L-blocksextending transversely of the tank on opposite sides of the plane ofdrawing, said blocks including horizontally disposed flanges definingbetween them an opening of varying width through which the sheet glassis to be drawn, the minimum width of said opening being at the centralportion of the tank and said opening increasing in width from itscentral portion toward opposite sides of the tank.

. 3. In an apparatus including a tank containing a molten glass bath andincluding a refractory structure defining a drawing chamber extendingacross the tank above the bath, said refractory structure being shapedto provide a sheet-glass-receiving opening extending across the chamberabove the bath and leading upwardly into said chamber, and means fordrawing sheet glass upwardly from the glass bath through said opening,portions of the refractory structure defining the opposed sides of theopening being inclined relative to one another outwardly from centralportions thereof, the lines of inclination of said sides being insubstantially horizontal planes whereby said opening increases in widthfrom its central portion toward opposite extremities thereof.

4. In an apparatus including a tank containing a molten glass bath andalso including means for drawing sheet glass upwardly along apredetermined plane from the bath, and refractory members disposedacross the tank on opposite sides of the plane of drawing and havingsurfaces facing each other from opposite sides of said plane inproximity to the bath, said facing surfaces on opposite sides of saidplane diverging from one another from central portions thereof towardopposite sides of the tank, the lines of divergence being insubstantially horizontal planes.

5. In an apparatus including a glass drawing tank containing a bath ofmolten glass, means for drawing sheet glass upwardly along apredetermined plane from the glass bath, a draw bar defining with saidmeans the plane along which the sheet glass is adapted to be drawn,refractory members supported adjacent opposite sides of said plane andhaving opposed surfaces which define an opening above the bath throughwhich the sheet glass is drawn, each of said surfaces including acentral portion projecting laterally toward said plane, said surfaces onopposite sides of said plane diverging from one another whereby thedistance laterally from the plane to each of said surfaces increasesfrom the central portion of the plane outwardly in horizontaldirections.

6. In an apparatus including a tank with a molten glass bath therein,means for drawing sheet glass upwardly from the glass bath along apredetermined plane, refractory members including opposed edges disposedon opposite sides of the plane of drawing, said members being disposedimmediately above said bath in facing relation thereto and definingalong their opposed edges a drawing openin through which sheet glass isdrawn, the lower bath-facing surface of each of said members decreasingin width from its central portion in opposite directions whereby saiddrawing opening is narrower at the central portion thereof and increasesin width toward its opposite extremities.

7. In an apparatus including a tank with a molten glass bath therein,means for drawing sheet glass upwardly from the glass bath along apredetermined plane, spaced refractory members disposed on oppositesides of the plane of drawing and defining between them a drawingopening through which the sheet glass is drawn, each refractory memberhaving a lower substantially horizontal surface disposed in proximity tothe upper surface of the bath in substantially parallel relationthereto, said lower surface havin its greater width along its centralportion and decreasing in width toward its opposite extremities.

8. In an apparatus including a tank with opposite side walls andcontaining a molten glass bath, means defining a drawing plane upwardlyfrom the bath along which the sheet glass is adapted to be drawn,refractory members disposed on opposite sides of the plane of drawingand extending substantially from one side wall to the other, eachrefractory member having an upright flange substantially parallel tosaid plane and having a horizontal flange directed laterally toward saidplane, said horizontal flange having a lower plane surface facing themolten bath in opposed parallel relation thereto and decreasing in widthfrom its central portion toward said side walls of the tank.

9. In an apparatus including a tank with a molten glass bath containedtherein, means for drawing a glass sheet upwardly from said bath, anL-block arranged in proximity to the sheet,

said L-block having a horizontal lower flange projecting laterallytoward the sheet and terminating in an edge that faces said sheet, thesheetfacing edge of the flange projecting at its central portion towardsaid sheet glass and increasing in distance from the sheet glass inopposite directions toward opposite extremities of the flange,

10. An L-block for inclusion in a drawing chamber of an apparatus inwhich glass is adapted to be drawn, said block having end portionsadapted to be supported in the apparatus, said block having a rear sideto face away from the chamber and a. front side to face sheet glass tobe drawn, said L-block having a lower horizontal flange, the front edgeof said flange having surface portions converging forwardly to fomn aforwardly projecting portion at the central portion of the flange andproviding varying horizontal width of the flange.

LURTY B. WHITE. FOREST S. THARP.

